Stackable ladder



FIG. 1 is a top front perspective view of a stackable ladder showing mynew design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a right-side elevation view thereof;

FIG. 4 is a top plan view thereof; and,

FIG. 5 is a bottom plan view thereof.

I claim the ornamental design for a stackable ladder, as shown anddescribed.